I’ve been using Netbeans for the last month, since their Beta 1 release. In a word, it’s fantastic. TextMate is a good Ruby editor but Netbeans goes far beyond it to offer code completion, integrated RDoc, Rake and Rails integration, refactoring (well, what little refactoring can be offered with a dynamic, untyped language) and tons of other features which offer serious value to Rubyists. I discover something new every time I open a new menu to explore. Check it out if you have a chance.